Maintenance workers were mistakenly on the wrong track when an Amtrak passenger train struck a large piece of railway equipment on Sunday near Philadelphia and killed two people, according to CNN.

The network cited an unnamed source in reporting that the train hit the crew after a "colossal" error left them on an active track.

Investigators on Monday from the National Transportation Safety Board were analyzing an event data recorder and video recordings recovered after the front of the train went off the tracks in Chester, Pennsylvania, about 15 miles southwest of Philadelphia.

The accident on Sunday morning also injured 35 people and left service suspended for much of the day along the busy corridor between Philadelphia and New York.

Steve Forbes, the U.S. publishing executive and two-time former Republican presidential hopeful, told CNN on Monday he was riding in the last car of the train that crashed.

"It was a matter of nanoseconds, but you felt the train was coming to a screeching halt, then it eased up a bit, then another screech," Forbes said. "There was coffee flying everywhere. There was the smell of smoke."

The locomotive engineer was among those on board the train taken to hospitals with injuries, none life-threatening, the NTSB said.

Forbes said passengers determined there was no fire and decided to stay inside the train car to avoid contact with live electrical wires outside. They did not receive instructions until first responders made their way to the final car about 30 minutes later, he told CNN.

Amtrak spokesman Mike Tolbert said the railroad was operating its normal schedule of train service along the busy Northeast rail corridor on Monday. He referred all other questions to the NTSB, which did not immediately respond to a request for comment.

The crash was the latest in a series involving the U.S. passenger rail carrier and occurred a few miles south of the site of a 2015 derailment in which eight people were killed.